A laser range finding apparatus of this kind is known from German patent publication DE 43 40 756 A1. With a laser radar of this kind one can not only determine the range of the objects struck by the light pulses but also the angle at which the object is arranged with respect to a predeterminable reference direction in space. The object's range is determined, starting from the measured pulse transit time, by taking account of the speed of light. In this arrangement the accuracy of this range determination is essentially dependent on the three following influencing parameters:
a) the resolution of the time measuring unit associated with the electronic control and evaluation system, PA1 b) the noise which is superimposed on the received signal, and PA1 c) the accuracy of the compensation which takes place in the electronic control and evaluation system of transit time measurement errors resulting from the signal dynamics.
A statistical measurement error results from the first two influencing parameters a) and b), which can be reduced by average value formation over a plurality of measurements. More critical is the third influencing parameter c), which is primarily to be attributed to the fact that the linear range of amplification of the pre-amplifier, which is as a rule connected after the opto-electronic photodetector, is restricted in comparison to the signal dynamics which arise in practice. Accordingly, the compensation of the transit time measurement errors which arise as a result of the signal dynamics in dependence on the measured peak value of the received light pulse on the basis of correspondingly determined correction values, as effected in the laser radar known from DE 43 40 756, only leads to the desired result in a relatively small range of modulation. If, in contrast, a modulation of the pre-amplifier takes place beyond its linear amplification range, then saturation effects arise which can, in particular, bring about an extended time duration of the output signal of the pre-amplifier. This can lead to transit time measurement errors, which can no longer be compensated by the peak value detection. This can, in particular, be the case when the trailing flank or the flank arising at the end of the output signal is also used for the transit time determination. In addition to this comes the fact that these effects are strongly dependent on temperature, voltage and batch.